A movement measurement device utilizing an optical sensor is described in the document US 2009/0248351. A mobile element moves in a direction perpendicular to the direction of emission of a light beam and a linear optical sensor with a pixel array of CCD (Charge-Coupled Device) type or CMOS (Complementary Metal Oxide Semiconductor) type stores the data obtained in this way relating to the luminous flux transmitted and partially blocked by the mobile element. The analog information from the sensors is converted into digital data that is integrated into a calculation module that determines the position of the mobile element from the latter data.
Such a device has disadvantages, in particular conversion of all of the analog information from the sensor into digital data. Analog noise is added to the errors and to the digital conversion noise. This undesirable noise limits the dynamic (signal to noise ratio) of the measured signal. Furthermore, conversion necessitates a non-negligible calculation time and a non-negligible calculation capacity.
In particular, when the device is used in a microphone, the background noise and analog-digital conversion are considered the main factors limiting the dynamic.
It would therefore appear advantageous to circumvent the analog dynamic limit and to limit as much as possible the drawbacks of analog-digital conversion.